Satan's Daughter
by Lamay
Summary: Just a story of what I think it would be like if Rin and Yukio had a sister. I own nothing, the characters belong to their rightful owner but I own Kaida. First story so it's probably not to great. Rated T for now, that may change as I go on. Leave a review if there's anything I need to fix. Need a better title but this'll do until I think of a better one. Follows the manga, kinda
1. Chapter 1 - Arrival

**You know those fanfics where the writers OC is always some relation to the main character or a popular character that is always more powerful than the character themselves? That's pretty much what this is. Honestly, where is the fun in a fanfic in one that isn't?**

 **But you know, if you don't like it, then why are you here?**

* * *

I'm fifteen years old and I'm Satan's only daughter. My two brothers and I were born of a human mother who died only moments after we were born. Yukio is the youngest and was born with no demonic powers so he is either a full human or most human, only time will tell with him. Rin is the middle child and I believe that he is roughly half human half human, more or less. I'm the oldest and I am a full demon, my name is Kaida. While still in my mother's womb, the demon blood took over the human blood, so I was born a full blooded demon. Not that I'm complaining, when I learn to control my powers fully I will be a force to be reckoned with.

I remember Shiro always had his hands full trying to keep both Rin and me in check although Rin wasn't as hard to deal with as me. He had his flames sealed within the Kurikara at birth so all the physical features of a demon or the flames. My powers weren't sealed as the only thing available was the Kurikara, so I still had the physical features and flames. When I was three years of age I had discovered my flames, most demonic children are smarter than the average human child. Shiro's method of keeping me in line wasn't the best. Each time I did something he disagreed with he would spray me with water mixed with holy water, so it didn't burn but gave of a sting.

Then at the age of five Shiro realised that I would only get more troublesome as I aged, I was already starting to rebel against him so it was obvious I was going to continue. So he made a decision to send me off to live with his friend that goes by the name of Mephisto Pheles. In Gehenna we know him as Samael, the Demon King of Time and Space and second in Gehenna's hierarchy. He would be able to raise me the way a demon child should be raised. He knew that demon children were naturally more curious and helping raise a few of his younger brothers, he knew exactly what to do.

I lived there for about a year then Satan sent one of the Demon Kings to take me to Gehenna and with Mephisto being Mephisto, he agreed. He wanted to see how much different I would turn out than my two brothers. In Gehenna, I spent time with different Demon Kings learning about demons, all but Samael and Lucifer. So Satan taught me about the Light demons as well as the Time and Space demons. Nothing in Gehenna resembles a human, everything has a different form. My usual form consisted of an electric blue coloured dragon and I had the ability to change my form into different creatures like Satan can, I had inherited more than just his flames. I lived in Gehenna for nine years then left for Assiah through the Gehenna Gate I had learnt to summon.

* * *

What a great place to appear in. It was my first time being in Assiah after nine years and I arrive in an alleyway. Fairly dirty but being in a busy Japan city, what do you expect? As I was still in my demon form, I couldn't exactly waltz up or walk down the street. Sure, some people wouldn't see me but the ones that could, would make a scene. I couldn't walk up in my human form either as Rin and Yukio probably wouldn't remember me, but Shiro would. So, I would take on a new look. I've heard that the Akita Inu dog is well respected around here so I decided I would take the form of one. So with my tail in the air and my head low, I walked out of the alleyway and made my way down the street. A few people looked at me but most ignored me. Some kids walked up and tried to pet me and I wasn't exactly sure about this so I tried to avoid them. I ran around for a while eventually finding what I was looking for.

The Monastery didn't really look any different from what it had all those years ago. Looking at it, I wondered if there would be any demon repelling spells around it. Taking in a deep breath, I slowly walked up to the gates. I put one foot over and nothing happened. I exhaled and then jumped when a voice spoke. "Hey! Where did you come from?" I let out a noise as I jumped in the air, looking around franticly. My eyes landed on a boy with messy, dark blue hair and blue eyes.

It was Rin.

I barked and wagged my tail, trying to look friendly. He started to walk up to me and I stayed where I was as I wasn't entirely sure what to do. Kneeling down in front of me, he held his arm out expecting me to sniff it.

"Who do you belong to? I haven't seen anybody here with an Akita before." I heard a door open and some footsteps walking towards us. Looking over Rins shoulder, I noticed this boy had brown hair, blue eyes like Rins but he wore glasses. This had to be Yukio.

"Rin, what are you doing out here? We are about to start eating… Is that a dog?" Yukio pointed directly at me and Rin nodded.

"Yeah, isn't it cool? Wonder if the old fart will let us keep it." I frowned at what Rin had said. I am not an it, I'm a girl. Of course, in my current state I couldn't talk so I couldn't correct him. I watched as Yukio walked towards both of us and stopped behind Rin. He looked into my green eyes and I looked back into his blue ones. I couldn't help but notice how much they had grown, I know it's been years but wow. Yukio patted Rins shoulder and spoke as he made his way back inside.

"Hurry up, the food will get cold." Yukio walked back inside with Rin following shortly behind him then just as he was about to walk in, he turned around and called me.

"Come on, I'm not leaving you out here." He held the door open and with that, I ran inside to see what would wait on the other side.

Inside the monastery hadn't changed at all. I walked beside my brothers who were arguing about something. I wasn't really paying attention but then they stopped at a table, people who I assumed were exorcists, were sitting around it eating some kind of food. Being in Gehenna for so long I had forgotten what food in Assiah was like. "So you've decided to come and join us? Say, who's the dog?"

"Yes father. I don't know who the dog is, I went to get Rin and he was with this dog." Yukio seemed to speak calmly, is he always like that? Wait, father? I hadn't really taken note of who the exorcists were but if he said father, then Shiro was here. Spotting him, I noticed he hadn't changed one bit.

"A red and silver brindle Akita isn't that common." Shiro said as he walked up to me. Something about him seemed a little bit off, he was just looking at me. "Does she have a name?"

"How do you know it's a girl?" Rin said exactly what I was thinking. I never saw him look… well, _there_. Shiro laughed a bit. "Well if she was a male, there would be something there."

Rin huffed. "Yeah well as far as I know, she doesn't have a name."

* * *

So after they all ate, they all argued over what the name for the new dog should be and eventually they agreed on Inazuma. I didn't really have the interest as to who picked it but it's not like I had a say in the matter. Eventually they all did their own thing and so I followed Shiro. I didn't particularly want to talk to him but I did have a few questions that needed to be answered. I watched him stop at a door and pull out a key. This must be one of those magic keys that take you to different areas. As he put the key in the lock, the door opened with a slight creak, there was a stairway going down. I walked silently behind him and I noticed that the only source of light was provided by candles as the room itself was very gloomy. I watched him stop at a chest and pull out another key, unlocking the chest that has something hidden inside.

"So I see you've kept his sword." I spoke. Shiro didn't turn around but simply replied, "I had a feeling it was you."

During that time I had shifted into my human form and I stood beside him with my hands in the pockets of the jacket I was wearing. His head turned to look at me, looking me up and down. "You've grown up quite nicely, although you could try to tame that blonde hair of yours." He smiled slightly as he spoke. I ran a hand threw my short and unusually blonde hair and my vivid green eyes looked at his red ones.

"What I do with my hair has nothing to do with you, it just kinda sits like this. The bit at the top doesn't sit down anyway." I said while pointing to antenna-like piece of hair standing upright. "Anyway, does Rin know? About us I mean." Shiro shook his head.

"No, I still haven't told him. I don't know how to bring it up exactly."

I sighed. "You need to tell and you need to be the one to tell him. I can't exactly waltz up to him like this. 'Oh hey Rin, you might not remember me but I'm your older sister, also you're the son of Satan. Congratulations.'" My voice practically screamed sarcasm during that last part and I folded my arms. Shiro just stood there not saying anything and this angered me. "Don't just stand there and say nothing, when do you plan on telling him? Because the longer you leave it, the harder it will be." I got a nod out of him at least.

"The timing hasn't been right. How am I supposed to tell him when he doesn't even think demons exist in the first place?" He asked.

I shrugged. "I dunno you gotta work that out for yourself." His eyes once again looked me up and down. "What's with the clothes anyway?" I frowned and looked at the clothes I was currently wearing. Sure they weren't the cleanest but why did it matter to him? The t-shirt had the AC/DC logo on it with a black jacket that I always left unzipped on top and my pants were just a black, baggy pair of tracksuits.

"There's nothing wrong with what I'm wearing. I haven't worn shoes or socks in years; I think going barefoot is more comfy. It's got nothing to do with you in the first place." I morphed back into the Akita and made my way to the stairs but stopped halfway up. "My point is you need to tell Rin. Because when _he_ comes, Rin won't know what's going on." I ran up the stairs leaving Shiro behind, I had said what I needed to and I didn't want to talk to him anymore.

* * *

 **So this is chapter one. I won't tell you to favourite or follow as if you don't like it, then I will respect that. But if you could leave a review, that would be nice. Whether it's to tell me how much you like it or how much you hate it. Criticism is welcome as I feel like that will help me to improve my writing. Any review is a good review.  
I'm still new at this, so tell me if I need to fix anything! :)**

 **I also don't update at any particular time. As I'm a fairly cruisy person, I will do it at my own pace.**


	2. Chapter 2 - Truth

**Just to clarify, the OCs real name is Kaida. The name 'Inazuma' is the name that Rin and the group gave when they found her because they didn't know who she was, so they didn't know her real name. Although after this chapter, people will be calling her Kaida and not Inazuma.**

 **So there's a bit of swearing in this chapter and a bit of violence as well. It's not really that bad but it could be a lot worse. So if it's not your cup of tea, then kindly buzz off. Anyway, here's chapter two! :D**

* * *

Not even a year had passed since I arrived here. Nothing interesting happened, everybody here except for Rin and Yukio knew who I really was so I didn't really need to be as secretive. That and Rins powers still haven't awakened yet.

So like usual, these daily walks with Rin were quite boring. Although something did happen today, we had an encounter with a group of teenage boys that were killing and chopping the legs off pigeons for fun and this didn't sit too well with Rin. "Oi! What the hell do you think you're doing?" He shouted at them.

One with white hair and a few piercings that I assumed was the leader, turned around. "What does it look like? We're cleaning up the street. These shitty birds just fly down for food without even suspecting anything!"

Even I thought this was a bit over the top and that's coming from a demon. Just as they were about to get back to what they were doing, from the corner of my eye I saw Rin run towards them and land a decent punch on the leader's cheek and of course this led to the other three joining in. I just sat and watched as the whole fight was happening and as much as I would love to, I couldn't join. If I were to bite one, Rin would get in trouble I would be ordered to be put to sleep. Not that I would actually let that happen. Kicks and punches were being thrown out and eventually one of the cronies realised they wouldn't win, even against one guy. Which is actually pretty embarrassing.

"Come on guys, let's get outta here! This guys a demon!"

Unsteadily, they got to their feet and ran off. I walked up beside Rin and sat down as he caught his breath. "I did it again Inazuma. Why do I always get into fights?"

I looked up at him then looked ahead, making a few mumbles that made Rin smile. "Come on, let's go home. I'll have to deal with the old man sooner or later, but later sounds like a better option."

* * *

Rin opened the doors to the monastery and as it was fairly quiet, so he assumed everybody must be eating. We made our way to the table and there was everybody, sitting down eating food. So Rin just sat down in a spare seat and I sat laid down under the table.

"So Rin, did you get a job this time?" I heard Shiro ask. I could just picture Rin become nervous at this, as obviously he didn't get a job.

"Um, well actually-"

"I bet he got into a fight, he looks like he's injured." Yukio cut Rin off and I laughed quietly to myself as I find it quite funny when Rin gets annoyed or angry.

"You did what!?" Shiro yelled. I heard Rin let out a quiet noise then heard a quiet clutter and saw a pair of chopsticks on the floor; my guess would be that Shiro threw them at Rin. Yet he tells Rin he has anger issues.

"You foolish boy!" Shiro continued. "Do you not realise that one day you will have to leave here and make a living on your own? How can you do that if you can't keep a decent job?"

I could just feel the tension in the air then Rin yelled, "I already know that!"

But then the stove caught my attention as it had flared up with some blue fire, fire that I hadn't caused. So this had meant that Rin did inherit his flames, and that his sword that was sealing his powers wasn't working as well as it used to. Things were bound to get more interesting.

I assumed Shiro would probably think that I had caused it, but I hadn't done anything since I've been here so I would need to tell him I didn't do it.

There was a silence for a few seconds that seemed to last longer until Shiro broke it. "Yukio, please go and tend to your brothers wounds."

I heard Yukio reply with 'yes father' then they walked off.

* * *

The next morning was a little weird, I found Rin in his room attempting to put on a suit but struggling with the tie. "Ah screw this, I'm just gonna leave the tie off. I'll go casual-formal."

Then he made his way out, a little grumpy might I add and walked outside. On the way out we saw Shiro waving goodbye to a little girl who had been having problems with demons. "It must be so hard to get rid of things that don't exist." Rin commented.

"Nonsense child, demons do exist. You just don't want to believe it. What's with the get up?" Shiro asked. I saw Rin's cheeks go a bit red as he answered.

"Well after yesterday, I thought I might go for that job interview that you mentioned."

I zoned out after a while, Shiro helped Rin tie his tie and made some fun of him. "Ah shut up, you stupid old man. Stay there Inazuma, I'll be back in a while."

Both Shiro and I watched as Rin walked out the gate but stopped briefly just to shoo away a Coal Tar then continue on his way. So his powers were awakening, Shiro's eyes grow wide with worry.

"Shiro, I'm going to go with him. He was the one who made the stove flare up, not me. I'm sure you also noticed that he saw the Coal Tar."

Shiro nodded, I could feel his uncertainty. "I was just going to ask if you could. Stay hidden unless something comes up."

I looked up at him. "You still haven't told him have you?"

Shiro didn't move for a good while but then shook his head. "I should've ages ago. He will eventually work out that he's not a normal human if we continue like this. When he gets back, I'll tell him."

I just nodded and ran out the gate before he had time to say anything else.

* * *

I followed Rin from a distance, hoping he wouldn't turn around and notice me as he'd just end up taking me back home. Just like when I first came here, I had to avoid all the kids trying to pat me and all the mothers trying to kick me away because I'd give their kids a disease. If only they knew what I could really do. During all this, I lost sight of Rin. Surely he couldn't be that far ahead, he's not the fastest walker. I figured that because Rin never turned anywhere, I should go straight and I'd eventually catch up to him.

But I didn't have to run far to see a blue flash from the corner of my eye, nothing here makes a flash like that. Then three boys ran past me and they looked kinda scared. "Shit! Let's get outta here!"

I don't know how this kid managed it, but he actually managed to trip over me and I fell to the ground with a yelp. How could the idiot miss seeing me? "Get out of the way you stupid dog!"

I gave off a confused expression and growled as he ran off. Wait, were they the boys from yesterday? That would be a bit odd; surely they must just look like them. Oh well, I got up and shook the dirt of my fur then made my way down the alley where the blue flash came from. As I got closer, I saw Rin on the ground with a possessed boy walking towards him. Then I noticed that he was the ringleader from the group yesterday, meaning that those were the right boys. "It seems like I was right about you after all."

What was he right about? The only thing that's wrong with Rin at the moment is that he's covered in blue flames. Then it clicked, Rin's covered in blue flames. Then the possessed boy knelt down in front of Rin. "That flame is none other than the flame of Satan. Let's go, my young prince. Lord Satan is waiting for you."

Nope. No way am I sitting around for Rin to be taken to Gehenna yet, it's still too early. I leapt over Rin and lunged at the boy successfully, grabbing his shoulder and tackled him to the ground. I shook him a few times to make sure I'd mangled it properly so that it would take a bit longer than usual to heal. I walked back to Rin with my hackles raised and my tail in the air to try to look aggressive. Hey, I had to try to keep my dog-like appearance. Rin just watched as the whole scenario unfolded but he managed to speak. "What are you doing here Inazuma? I told you to stay home!"

I just made a mumble noise in response and then the boy got to his feet shakily, holding his shoulder. I made a note of the goat-like horns protruding from his head and the skinny arrowhead tail. "You do know that she isn't actually a dog right? Isn't that right, Miss Kaida?" He spoke as he pointed to me.

"How can she be anything but a dog? Her name isn't even Kaida!" Rin still looked confused and now that his powers have been awakened, why continue to hide it from him. So I finally spoke. "He's right Rin, you probably won't actually believe this but I'm your sister. You and Yukio aren't twins, but a set of triplets."

Nothing I said was being taking in by Rin so I just assumed my human form. I assumed he was in shock or something but then he spoke. "Why did you just turn from a dog into a human? And what is with the fucking tail?"

Yup, nothing was taken in. "Fuck it, that's enough from you Kaida." The boy spoke. "Move out of the way, I need the boy."

I snarled in response and stood my ground until I heard a chant start. "There is evil in their hearts…"

I started to panic but then I heard Rin whisper 'father' and I knew it must be Shiro. I also noticed the boy had started freaking out pretty badly but wasn't too keen to show it. Instead he frowned and yelled, "You… Are you an exorcist!?"

Shiro simply smiled and continued, "Blessed be the lord."

I crouched next to Rin and watched as the boy charged towards Shiro, only to be exorcised on the spot. Rin's flames had dwindled and eventually died out; Shiro looked at the both of us. "Rin, are you calm yet?"

I couldn't help but reply sarcastically, "Yes, he's so calm he could go to sleep. What the fuck does it look like!?"

Rin asked what was going on and Shiro gave him the run down on Assiah and Gehenna, forgetting to even ad me into the story.

"You, Yukio and Kaida here," He pointed at me and continued, "are the offspring of a human mother and a demon father, but not just any normal demon but the God of all demons. You are the child of Satan."

* * *

 **So that's it currently. Dunno when he next chapter should be out but since I feel like I'm on a roll, it should be fairly soon. Anyway, review and tell me what you think, let me know if I've made a mistake or something. Have a good day/night depending on where you are in this world and the next one should be out soon, but no promises. ^-^**


	3. DON'T GET YOUR HOPES UP!

**This is not a new chapter but I'm really just here to say that I think I might redo the first two chapters before I upload any more, not that I've uploaded anything in a year or close to a year. I will be continuing this but I feel like there's a shit-ton of things that need fixing**


End file.
